1. Field of the Invention:
This invention relates to a process for production of high-purity metallic iron.
2. Description of the Prior Art:
The conventional process for production of high-purity metallic iron has been mostly an electrolytic refining process which electrodeposits high-purity iron on a cathode plate in a sulphuric acid or hydrochloric acid bath using a comparatively high-purity metallic iron, for example a mild steel, as an anode.
However, the following disadvantages are found in the conventional electrolytic process.
(1) Electrolysis in strong acids, such as electrolysis of zinc is impossible because iron ion is a more base metallic iron than H.sup.+ ion and has a low hydrogen overvoltage;
(2) Operational control of electrolytic bath is difficult;
(3) Maintenance of electrolytic bath over 3 of pH value precipitates iron hydroxide to cause oxidation of Fe.sup.2+ ion;
(4) Intrusion of any nobler metal ions than iron ion, such as copper ion, into the electrolytic bath cannot yield high-purity metallic iron;
(5) Dendritic electrodeposit of deposited metallic iron on the cathode often prohibits continuation of successive electrolysis or hinders a high current efficiency; and
(6) Large amounts of power and labor required for finely grinding metallic iron electrodeposited on the cathode plate into particles under 40.mu. in hydrogen or inert gas stream to obtain high-purity iron powder increase the production cost of high-purity metallic iron and thus limiting its application field.